Dead Zones in the Ocean – Science Nation

August 15, 20196

JACK BARTH: It’s a little bit bumpy today.
We’ve got the first of the fall storms kind of sweeping through. So we’re just going to
go out to about 50 meters of water. MILES O’BRIEN: Oceanographer Jack Barth has
had plenty of bumpy rides off the Oregon coast, launching and retrieving these underwater
gliders. From April to October, they gather data to help answer questions about the health
of the world’s oceans. BARTH: Alright, buddy, we’re going to go with
the swell. Alright, here we go. Next one. Ready? Now. The main things we are measuring
are temperature, salinity, and importantly, the dissolved oxygen of the water. And that’s
what tells us how that low oxygen zone looks. O’BRIEN: With National Science Foundation
funding, Barth is studying low oxygen, or “dead” zones, which appear each summer off
the Oregon-Washington coast. BARTH: So in 2006, we actually went to zero
oxygen, and it extended many miles across the sea floor. And, that’s when we partnered
with the Oregon Department of Fish and Wildlife to send a camera down on a remotely operated
vehicle. And we got these images of dead crabs everywhere. O’BRIEN: Worldwide, ocean dead zones now number
about 400. The major manmade cause is agricultural runoff, from rivers into the ocean. In addition,
winds and currents move nutrient rich, but oxygen poor water, from the deep ocean to
the coast. Microscopic organisms called phytoplankton thrive, but then die, decompose and the cycle
continues. Climate change may also come into play. BARTH: We think there’s two scenarios that
global warming is potentially affecting this. Out in the deeper ocean, there’s measurements
that show that the oxygen levels are going ever so slightly down with time. When that
water is brought to our shore, it’s already low in oxygen. O’BRIEN: Global warming may also be influencing
wind patterns and changing ocean circulation. Barth says these smart robots provide new
insight to understand our oceans. BARTH: To me, it’s opened this whole new view
under the sea. I think it’s really revolutionized how we can keep a tap on what’s going on out
there. O’BRIEN: For Science Nation, I’m Miles O’Brien.